The extensive use of heavy-duty diesel engines in underground mines has raised concerns about the potential adverse health effects arising from exposure of miners to diesel exhaust. Of particular concerns is exposure to diesel particulate matter (DPM), which is largely in the respirable range and contains mutagenic and carcinogenic organic compounds. The objective of this continuation proposal is to evaluate the effects of diesel emission control devices on the in-mine concentrations of DPM and health-related DPM-components such as polynuclear aromatic hydrocarbons (PAH) and mutagenicity in order to assess the effects of these devices on air quality of the underground mine environment. This project is a collaborative study involving Michigan Technological University (MTU) and the Bureau of Mines (BOM). The specific aims of this proposed project are: 1) collection of DPM in underground mines where diesel emission control devices are being used; 2) extraction and quantification of the organic material associated with the DPM; 3) determination of the mutagenicity associated with the organic fraction using the Ames assay; and 4) quantification of selected mutagenic and carcinogenic PAH associated with the organic fraction. A qualitative study will also be conducted on semi-volatile organics collected on polyurethane foam (PUF). The BOM is planning on conducting field tests of three emission control devices in two configurations. Disposable exhaust filters will be tested in an underground coal mine using diesel haulage vehicles. A catalyzed diesel particle filter and an oxidation catalytic converter will be tested together on a load-haul-dump vehicle in an underground molybdenum mine. At each mine, samples will be collected by BOM personnel for chemical and biological analyses at MTU. Hi-volume samplers fitted with inertial impactors to remove non-diesel particles will be used in conjunction with PUF to collect both DPM and vapor phase organics. Samples will be collected the haulage road and section intake. The number of samples collected will depend upon whether or not a control device is installed on the vehicle. The DPM and organic fraction levels will be determined at MTU for each sample. Organic fraction mutagenicity will be determined using the microsuspension version of the Salmonella/microsome mutagenicity bioassay (Ames assay). Quantification of up to 20 PAH and nitro-PAH in the organic fraction will be conducted using high performance liquid chromatography and fluorescence detection. Analysis of these data will determine the benefits to be derived from control device usage. The data will also be compared to those obtained in the current study on both in-mine diesel-related concentrations without control devices) and laboratory test cell-generated data with the control devices.